1. Field of the Invention
The present invention relates to a flexible tube used for an insertion section of an insertion apparatus of an endoscope, etc. which, for example, is inserted into a hole of a passage, etc., and an insertion apparatus including the flexible tube.
2. Description of the Related Art
Jpn. Pat. Appln. KOKAI Publication No. 2013-097327, for example, discloses a flexible tube that includes a helical tube, and an outer tube covered on an outer side of the helical tube. The helical tube includes a closely-wound region including a closely-wound portion having a tight contact force applied on adjacent parts of a wire member adjacent to each other along a longitudinal axis and a sparsely-wound portion where the adjacent parts of the wire member adjacent to each other are separated from each other along the longitudinal axis. The closely-wound portion and the sparsely-wound portion are arranged alternately along the longitudinal axis.